It is known to impart to protein -- fat produces the characteristics of smoked flavor by direct subjection of said products to the action of curing smoke obtained as a result of uncompleted combustion of cellulose-lignin material. The draft method imparts to products indeed the expected taste and smell of smoked flavor but at the same time it contaminates them with superfluous and harmful components to which belong first of all nitric bases and certain volatile acids imparting a foreign smell to the products being treated, as well as carcinogenic hydrocarbons, benzopyrene and benzophenathrene derivatives.
Furthermore, the smoking by means of curing smoke on a large commercial scale is a technologically onerous process, difficult to standarize and automate for continuous production lines requiring expensive devices and great stores of definite wood material indispensable for the preparation of smoke.
The above disadvantages and inconveniences are the reason why the draft method of smoking is gradually being abandoned and replaced by so-called smokeless curing with the aid of smoking agents which when added to articles of food impart to them taste and smell properties more or less similar to that of products smoked according to the classical method but containing neither carcinogenic nor ballast substances.
Smoking agents are obtained from products of destructive distillation of wood or cognate raw-materials which is effected without air access or with air excess. Initially, as the raw materials, distillation water separated components obtained from the dry distillation of wood was mainly utilized; in the course of time distilled tar and smoke products formed during the pyrolysis of wood were used. There exists a series of methods of obtaining smoking agents from these raw-materials by way of distillation, extraction, fractionation or a combination of operations seeking the removal of harmful and undesired components and retaining only compounds or groups of compounds exhibiting suitable taste and smell properties, and antioxidant and bactericidal characteristics.
From smoking agents very high quality requirements are expected, the fulfilment of which is a fundamental condition for the acceptance of said agents by government authorities for their application to articles of food. Furthermore they should impart to articles of food the typical desired taste and smell of smoked products; they should exhibit antioxidant and bactericidal properties, and they are not allowed to comprise carcinogenic compounds in a quantity exceeding 1 part by weight per one million parts by weight of the article of food and they should be used in quantities of from a dozen or so to several hundred parts by weight of the agent per one million parts by weight of the product.
From among known smoking agents only a few of them fulfil the above conditions. Among them are the smoking agent obtained according to U.S. Pat. No. 3,445,248, U.S. Pat. No. Re. 27,670 and U.S. Pat. No. 3,903,267. These agents are obtainable by fractional extraction, with the aid of organic water-immiscible solvents, advantageously ethyl ether, of the condensate of curing smoke obtained in the process of destructive distillation of cellulose and/or lignin material, in air excess.
In the process according to U.S. Pat. No. 3,903,267 three usable fractions are isolated. As the first, the fundamental fraction, the fraction containing mainly phenol compounds of a molecular weight of above 140 is obtained. This fraction may be mixed with the second, the terpene fraction obtained during the further course of the extraction and containing compounds that do not form salt type combinations in a medium of a pH value of about 12.8, and with the third, the acid fraction containing lower carboxylic acids and forming the finished smoking agent. However, this method is technologically rather difficult and labor-consuming, and requires a complicated apparatus.